This invention is directed to sanitary napkins having flaps. More particularly, this invention is directed to an efficient apparatus and method of folding and securing these flaps during the process of making sanitary napkins.
Sanitary napkins having flaps extending outwardly from the longitudinal side margins are well known in the art. For example, U.S. Pat. No. 4,589,876 issued May 20, 1986, to Van Tilburg and U.S. Pat. No. 4,687,478 issued Aug. 18, 1987, to Van Tilburg disclose preferred sanitary napkins with flaps and are incorporated herein by reference to illustrate flapped sanitary napkin constructions.
It is also well known in the art to fold the flaps to overlay the main body of the pad during the manufacturing process. For example, in U.S. Pat. No. 4,759,754 to Korpman, an adhesive tab is used for maintaining the flaps in the desired disposition overlaying the backsheet during packaging. U.S. Pat. No. 4,701,178 issued Oct. 20, 1987, to Glaug et al. discloses a sanitary napkin having a single release strip which covers the centrally located adhesive of the backsheet and over which release strip the flaps are folded.
Alternative means for maintaining the flaps in a folded disposition prior to first use of the sanitary napkin by the wearer are shown for example, in U.S. Pat. No. 4,285,343 to McNair which discloses a sanitary napkin with flaps (side panels) that are folded over the upper surface of the central absorbent element for packaging. At the time of the first use by the wearer, the flaps are usually unfolded to facilitate installation of the sanitary napkin into the wearer""s undergarment. Adhesive patches on a garment facing surface of the flaps are covered with individual strips of release paper.
An alternative method of holding the flaps in place is to utilize the release strip paper present on the attachment adhesive located on the flaps. EP 0 347 319 B1 to Marsot and WO 88/04546 to Ternstrom disclose the use of a single release paper in the form of a bridging strip across the flap adhesive patches for maintaining the flaps in the folded disposition prior to the wearer""s first use of the sanitary napkin.
Two additional examples of this technique are shown in U.S. Pat. No. 5,800,654, to Davis et al. and U.S. Pat. No. 5,662,639 to Tanaka et al. In these methods the attachment adhesive on the flaps is applied in a conventional manner, i.e. via a transfer coating method and a single sheet of release paper acts both as a protective peel strip for the adhesively coated flaps and as a means to hold the flaps in their folded position.
Use of these methods has several drawbacks. These methods require accurate placement of additional adhesives and materials. In particular in the situation in which the flaps are folded onto the body-faceable side of the napkin, adhesives should not come in direct contact with the absorbent material of the sanitary napkin as doing so both adversely effects the absorbency of that material and results in dissatisfaction of the user as to the articles appearance and comfort in use.
Further, use of an additional strip to hold the flaps in their folded position requires additional expense for material at the time of construction and presents an inconvenience to the user in having to discard this material at the time of use. In addition, this method requires that the flaps be maintained in a substantially parallel position relative to one another. If one or both flaps become skewed during manufacture, the adhesive will not be correctly placed on one or both of the flaps, thus rendering it useless. One method of overcoming this problem is to make the peel strip quite large to accommodate this potential skewing, thus exacerbating the problems associated with cost and disposal of peel strip material.
Accordingly, it is an object of this invention to overcome certain problems of the prior art. Particularly, it is an object of this invention to provide a means to mechanically maintain the flaps in their folded position during manufacturing and to do so without the necessity of additional adhesives or materials.
In accordance with the present invention, there has been provided a novel apparatus for folding a web of flap material over the main body of a sanitary napkin. This apparatus comprises a conveyor means having a substantially fixed velocity for transporting the sanitary napkin, which napkin having a web of laterally extending flap material; a flap folding station for folding said flap material onto said main body of said sanitary napkin; an indexing means comprising a pair of spaced apart finger timing belts, each having a lug affixed thereto, and a finger means intermediate said lugs, said finger means having two ends, each end being mounted onto a respective lug, said finger timing belt imparting a varying velocity to said finger means and establishing repeatable linear and non-linear relationships between the velocities of said finger means and said conveyor means; a napkin folding station for folding said sanitary napkin such that upon completion of the folding, a transverse end portion of said sanitary napkin overlies said web of flap material; wherein: said finger means is adapted to contact and maintain said web of flap material on said main body of said sanitary napkin from said flap folding station to said napkin folding station and, wherein upon completion of the folding of said sanitary napkin by said napkin folding station, said finger means has a velocity less than the velocity of said conveyer means whereby said finger means and said napkin no longer contact one another.
Also provided in accordance with the present invention is a novel method of folding a web of flap material in a continuous manufacturing operation for making absorbent articles, comprising the steps of transporting sanitary napkins along a conveyor means, each napkin having a web of laterally extending flap material; folding said flap material onto said main body of said sanitary napkin; providing an indexing means having a pair of spaced apart finger timing belts, each having at least one lug affixed thereto, each said lug on one timing belt having a counterpart lug on said second timing belt, a finger means intermediate said counterpart lugs, said finger means having two ends, each end being mounted onto a respective lug and thereby resulting in the finger means being substantially orthogonal to both timing belts, said finger timing belts imparting a varying velocity to said finger means and establishing repeatable linear and non-linear relationships between the velocities of said finger means and said conveyor means; folding said sanitary napkin such that upon completion of the folding, a transverse end portion of said sanitary napkin overlies said web of flap material; contacting said finger means with the sanitary napkin to thereby hold said web of flap material on said main body of said sanitary napkin between said steps of folding the flap material and folding the sanitary napkin; and, removing said finger means from contact with said sanitary napkin upon completion of said step of folding of said sanitary napkin.